A type of endoprosthesis device, commonly referred to as a stent, may be placed or implanted within a vein, artery or other hollow body organ or lumen for treating occlusions, stenoses, or aneurysms of a vessel by reinforcing the wall of the vessel or by expanding the vessel. Stents have been used to treat dissections in blood vessel walls caused by balloon angioplasty of the coronary arteries as well as peripheral arteries and to improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Two randomized multicenter trials have recently shown a lower restenosis rate in stent treated coronary arteries compared with balloon angioplasty alone (Serruys, P W et al., New England Journal of Medicine 331: 489-495 (1994) and Fischman, D L et al. New England Journal of Medicine 331:496-501 (1994)). Stents have been successfully implanted in the urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others. The term xe2x80x9cstentxe2x80x9d as used in this Application is a device which is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.
One of the drawbacks of conventional stents is that they are difficult to position. In general, positioning a stent involves moving the stent to the desired position and then maintaining the position while the stent is deployed. Accurate positioning is critical to proper operation of the stent. For example, the use of such stents to treat diseased vessels at or near a bifurcation (branch point) of a vessel requires very accurate positioning otherwise, there is a potential for compromising the degree of patency of the main vessel and/or its branches, or the bifurcation point. Compromising the bifurcation point limits the ability to insert a branch stent into the side branch if the result of treatment of the main vessel is suboptimal. Suboptimal results may occur as a result of several mechanisms, such as displacing diseased tissue, plaque shifting, vessel spasm, dissection with or without intimal flaps, thrombosis, and embolism.
In light of the foregoing, it would be desirable to provide methods, apparatus and/or systems to increase stent positioning accuracy, particularly when used with bifurcated body lumens.
The present invention provides exemplary apparatus, systems and methods for accurately delivering and positioning a stent within a body lumen, particularly within a bifurcated body lumen. In one embodiment, a stent delivery system according to the present invention includes a catheter comprising a catheter body having a distal end, a proximal end, a longitudinal axis and a lumen. An expansion device, which in one embodiment is a balloon, is disposed near the catheter body distal end, and a stent having a side hole is disposed over the expansion device. An ultrasound transducer is disposed near the catheter body distal end and positioned for transmitting and receiving ultrasound signals through the side hole. In this manner, an intravascular ultrasound catheter and system is used to help properly position the stent, and properly align the stent side hole with a branch vessel.
The ultrasound transducer is disposed inside the expansion device, or between the expansion device and stent in alternative embodiments. Preferably, the ultrasound transducer is adapted to be axially translated along the longitudinal axis and/or rotated relative to the longitudinal axis. In this manner, the ultrasound transducer may be used to image surrounding fluids and tissue to assure proper stent alignment.
In some embodiments, the stent delivery system further includes a transducer housing to which the transducer is coupled. The housing has distal and proximal ends, with a passageway passing therethrough. The passageway has a guidewire partially disposed therein in one embodiment. The housing proximal end is coupled to a drive cable, which in one embodiment is adapted to rotate the housing relative to the catheter distal end. A controller may be included, coupled to the transducer, to facilitate system operation.
The present invention further provides methods of positioning a stent having a side opening. In one embodiment, the method includes providing a stent delivery system ostensibly as described herein, positioning the stent delivery system in a body lumen, imaging the body lumen with the transducer to locate an ostium of a branch vessel, and aligning the stent side hole with the ostium. In this manner, the use of ultrasound imaging facilitates proper stent side hole alignment with the branch vessel.
In one embodiment, the ultrasound transducer is adapted to rotate relative to the longitudinal axis. The imaging further includes rotating the transducer to image a cross section of the body lumen. Similarly, in one embodiment, aligning the stent side hole includes axially translating the stent along the longitudinal axis and/or rotating the stent about the longitudinal axis. In some embodiments, a body lumen guidewire is introduced, and the catheter is advanced over the guidewire to be near the branch vessel.
In one embodiment, the stent delivery system is conveniently part of a kit, which includes instructions for use setting forth a method for positioning the stent in a bifurcated body lumen so that the side hole is substantially aligned with an ostium of a branch vessel.